Multi vegetation model evaluation of the Green Sahara climate regime

Abstract

During the Quaternary, the Sahara desert was periodically colonized by vegetation, likely because of orbitally induced rainfall increases. However, the estimated hydrological change is not reproduced in climate model simulations, undermining confidence in projections of future rainfall. We evaluated the relationship between the qualitative information on past vegetation coverage and climate for the mid‐Holocene using three different dynamic vegetation models. Compared with two available vegetation reconstructions, the models require 500–800 mm of rainfall over 20°–25°N, which is significantly larger than inferred from pollen but largely in agreement with more recent leaf wax biomarker reconstructions. The magnitude of the response also suggests that required rainfall regime of the early to middle Holocene is far from being correctly represented in general circulation models. However, intermodel differences related to moisture stress parameterizations, biases in simulated present‐day vegetation, and uncertainties about paleosoil distributions introduce uncertainties, and these are also relevant to Earth system model simulations of African humid periods.

Global vegetation patterns of the past 140,000 years

“…Recent climate model simulations suggest that changes in dust could also be important (Pausata, Messori, & Zhang, 2016), although this result may have been an artefact of that particular model (Hopcroft & Valdes, 2019; Thompson, Skinner, Poulsen, & Zhu, 2019). A lack of sensitivity of modelled vegetation to rainfall in sub‐Saharan Africa may also contribute to the problem (Hopcroft, Valdes, Harper, & Beerling, 2017).…”

Dynamic Vegetation Simulations of the Mid‐Holocene Green Sahara

“…The vegetation simulated by LPJ‐GUESS may be compared with results from three previous first‐generation dynamic vegetation models (Hopcroft et al, ). In terms of the climate forcings, MH_gsrd represents a more comprehensive realization of vegetated Sahara because precipitation, temperature, radiation, and soil temperature forcings are all generated by a GCM.…”

Holocene Vegetation and Climate Dynamics in the Altai Mountains and Surrounding Areas

“…As a result, vegetation and ecosystems are sensitive to climate change. For this reason, investigating past changes in Holocene vegetation patterns at various spatial scales can be used for developing analogues of future vegetation composition and its response to changing climate dynamics under the current global warming scenario (Blyakharchuk et al, 2007;Feurdean et al, 2017;Hopcroft et al, 2017;.…”